Mobile communication systems were developed to provide voice service, ensuring the mobility of users. The mobile communication systems have extended their range of services to data service as well as voice service. Now the mobile communication systems can provide high-speed data service. However, since the existing mobile systems suffer from lack of resources and users demand faster services, an advanced mobile communication system is required.
In Voice over Internet Protocol (VoIP) of a mobile communication system, the overhead of control signals is one of significant factors that reduce VoIP capacity. Particularly, multiple retransmissions may occur at a cell edge. The resulting decrease of service quality and increase of overhead eventually degrades VoIP performance. To overcome the problem, a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)/LTE-Advanced (LTE-A) system defines a TTI bundling technique that transmits the same data continuously in multiple TTIs to thereby reduce a transmission error probability and increase VoIP performance at a service boundary area.